In facilities such as a thermal power station, an ironworks, and a boiler, a large amount of fuel such as coal, heavy oil, and extra heavy oil is used. In regard to sulfur oxide, nitrogen oxide, and carbon dioxide discharged by burning of the fuel, quantitative/concentration restriction on emissions has been required from the viewpoint of prevention of air pollution and global environmental protection. In recent years, carbon dioxide has been viewed as a problem as is a major contributor to global warming, and moves to suppress carbon dioxide emissions have been active worldwide. Therefore, various studies have been vigorously progressed in order to enable recovery/storage of carbon dioxide of a combustion exhaust gas or a process exhaust gas instead of emitting carbon dioxide in the air, and, for example, a PSA (pressure swing) method, a membrane separation concentration method, a chemical absorption technique using reaction absorption with a basic compound have been known as a method of recovering carbon dioxide.
In the chemical absorption technique, a basic compound that typically belongs to alkanolamines is used as an absorber. In the process of the chemical absorption technique, generally, with having an aqueous liquid containing the absorber as an absorbing liquid, the absorbing liquid is circulated by alternately repeating an absorption step of causing the absorbing liquid to absorb carbon dioxide included in the gas and a regeneration step of regenerating the absorbing liquid by causing the absorbing liquid to release the absorbed carbon dioxide (for example, see Patent Literature 1 described below). In the regeneration step, heating for releasing carbon dioxide is necessary, and, in order to reduce the operation cost of carbon dioxide recovery, it becomes important to reduce energy required for heating/cooling. In Patent Literature 1 described below, it is configured such that thermal energy is recovered from the recovery gas, using a heat exchanger provided at a passage of the gas recovered from the regeneration step, and that it is supplied to the regeneration step.
Further, for the purpose of reducing energy required in recovering carbon dioxide from the absorbing liquid, Patent Literature 2 described below uses, for the heating of the absorbing liquid, remaining heat of steam-condensed water that is generated from a regeneration heater for performing heat exchange between the absorbing liquid and high-temperature steam by drawing the absorbing liquid from the regeneration step. Further, Patent Literature 3 described below discloses that a stripping gas is introduced so as to be accompanied with carbon dioxide, in order to facilitate releasing of the absorbed carbon dioxide.